Diffuser case mixing chamber for a turbine engine

ABSTRACT

A turbine engine includes a compressor section, a combustor in fluid communication with the compressor section, and a turbine section in fluid communication with the combustor. Also included in the turbine engine is a mixing chamber. The mixing chamber is located between the compressor section and the combustor section and the mixing chamber is radially outward of a primary fluid flow path connecting the compressor section, the combustor section, and the turbine section.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.14/910,283 filed on Feb. 5, 2016. U.S. patent application Ser. No.14/910,283 is a National Phase application of International ApplicationNo. PCT/US2014/049334 filed on Aug. 1, 2014. International ApplicationNo. PCT/US2014/049334 claims priority to U.S. Provisional ApplicationNo. 61/862,276 filed on Aug. 5, 2013.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

This invention was made with government support under Contract No.FA8650-09-D-2923 awarded by the United States Air Force. The Governmenthas certain rights in this invention.

TECHNICAL FIELD

The present disclosure relates generally to turbine engine structures,and more specifically to a diffuser case for a turbine engine.

BACKGROUND OF THE INVENTION

Gas turbine engines are generally known and, when used on an aircraft,typically include a fan delivering air into a bypass duct and into acompressor section. Air from the compressor section is passed downstreaminto a combustion section where it is mixed with fuel and ignited.Products of this combustion pass downstream over turbine rotors drivingthem to rotate.

Turbine rotors drive compressor and fan rotors. Historically, the fanrotor was driven at the same speed as a turbine rotor. More recently, ithas been proposed to include a gear reduction between the fan rotor anda fan drive turbine. With this change, the diameter of the fan hasincreased dramatically and a bypass ratio, or volume of air deliveredinto the bypass duct compared to a volume delivered into the compressorhas increased. With this increase in bypass ratio, it becomes moreimportant to efficiently utilize the air that is delivered into thecompressor.

One way to increase the efficiency of the use of this air is to increasethe pressure at the exit of a high pressure compressor. This elevatedpressure results in a high temperature increase at the exit of the highpressure compressor. The elevated temperature at the exit of the highpressure compressor is known in the art as T₃.

In order to cool the high pressure compressor, as well as other turbineengine components with elevated temperatures, existing designs directcool air from other portions of the engine, such as a bypass flowpath,onto the components that are desired to be cooled. In some instances theair being utilized in this manner is too cool relative to thetemperature of the component, and the air will not provide propercooling unless it is conditioned to be the correct temperature.

SUMMARY OF THE INVENTION

A turbine engine according to an exemplary embodiment of thisdisclosure, among other possible things includes a compressor section, acombustor in fluid communication with the compressor section, a turbinesection in fluid communication with the combustor, and a mixing chamber,the mixing chamber is located between the compressor section and thecombustor section and the mixing chamber is radially outward of aprimary fluid flow path connecting the compressor section, the combustorsection, and the turbine section.

In a further embodiment of the foregoing turbine engine, the mixingchamber is defined by an inner diffuser case wall, an outer diffusercase wall, and a mixing chamber wall.

In a further embodiment of the foregoing turbine engine, the mixingchamber wall isolates the mixing chamber from a diffuser chamber, andthe mixing chamber wall includes a seal having local penetrations suchthat diffuser air can travel from the diffuser into the mixing chamber.

In a further embodiment of the foregoing turbine engine, the mixingchamber wall isolates said mixing chamber from a diffuser chamber, andthe mixing chamber wall includes a seal having local penetrations suchthat diffuser air can travel from said diffuser into the mixing chamber.

In a further embodiment of the foregoing turbine engine, the seal is afinger seal.

In a further embodiment of the foregoing turbine engine, the seal is asheet metal seal.

In a further embodiment of the foregoing turbine engine, the outerdiffuser case wall includes an opening for connecting to a bypassairflow passage such that bypass air enters the mixing chamber throughthe opening.

In a further embodiment of the foregoing turbine engine, the secondaryflow passage directs air from the mixing chamber to at least one turbineengine component.

In a further embodiment of the foregoing turbine engine, the turbineengine component is one of a tangential on board injection system and acompressor on board injection system.

In a further embodiment of the foregoing turbine engine, air enteringthe mixing chamber from the bypass airflow passage is overcooled air.

A turbine engine according to an exemplary embodiment of thisdisclosure, among other possible things includes a compressor section, acombustor in fluid communication with the compressor section, a turbinesection in fluid communication with the combustor, and a mixing chamberdefined within a diffuser case strut, the diffuser case strut isconnected to a turbine engine case via an inner diffuser case wall andthe diffuser case strut is connected to an radially inward enginesupport structure via at least an inner skirt, a cooled air inlet tubeextending from the turbine engine case into the mixing chamber such thatair entering the cooled air inlet tube is deposited in the mixingchamber.

In a further embodiment of the foregoing turbine engine, the diffusercase strut is located within a primary fluid flow path connecting thecompressor section, the combustor section, and the turbine section.

In a further embodiment of the foregoing turbine engine, wherein an aftedge of the diffuser case strut is a mixing chamber wall and isolatesthe mixing chamber from ambient air in the combustor section.

In a further embodiment of the foregoing turbine engine, the mixingchamber wall includes at least one metering hole operable to allowambient air from an adjacent engine component to enter the mixingchamber and mix with air deposited from the inlet tube.

In a further embodiment of the foregoing turbine engine, the cooled airinlet tube includes an inlet opening for connecting to a bypass airflowpassage such that bypass air enters the mixing chamber through the inlettube, the inlet opening is on an opposite end of the inlet tube relativeto an outlet of the cooled air inlet tube, the outlet of the cooled airinlet tube is in the mixing chamber.

In a further embodiment of the foregoing turbine engine, the mixingchamber further includes an outlet opening operable to direct mixed airout of the mixing chamber.

In a further embodiment of the foregoing turbine engine, the outletopening directs air from the mixing chamber to at least one turbineengine component.

In a further embodiment of the foregoing turbine engine, the turbineengine component is one of a tangential on board injection system and acompressor on board injection system.

A turbine engine according to an exemplary embodiment of thisdisclosure, among other possible things includes a compressor section, acombustor in fluid communication with the compressor section, a turbinesection in fluid communication with the combustor, and a mixing chamberdefined within a diffuser case, the diffuser case is located between thecompressor section and the combustor section and the mixing chamber isat least partially defined by a diffuser case strut.

In a further embodiment of the foregoing turbine engine, the mixingchamber includes a first opening operable to receive air from a heatexchanger, at least one second metered opening operable to receivemixing air from an adjacent turbine engine section, and an outlet

In a further embodiment of the foregoing turbine engine, the mixingchamber is isolated from a fluid flowing through a primary fluid flowpath connecting the compressor section, the combustor section, and theturbine section.

A method for cooling air according to an exemplary embodiment of thisdisclosure, among other possible things includes receiving overcooledair in a mixing chamber, the mixing chamber is the mixing chamber islocated between a compressor section and a combustor section and themixing chamber is radially outward of a primary fluid flow pathconnecting the compressor section, the combustor section, and a turbinesection of a turbine engine, receiving ambient air in the mixingchamber, the ambient air is warm relative to the overcooled air, mixingthe overcooled air and the ambient air in said mixing chamber such thata desired air temperature is achieved; and distributing mixed air to aturbine engine cooling system.

In a further embodiment of the foregoing method, the step ofdistributing mixed air to a turbine engine cooling system comprisesdistributing air to at least one of a tangential on board injectionsystem, a compressor on board injection system, and an exit rim of thecompressor section.

These and other features of the present invention can be best understoodfrom the following specification and drawings, the following of which isa brief description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically illustrates a gas turbine engine.

FIG. 2 schematically illustrates a sectional view of the turbine engineof FIG. 1.

FIG. 3 schematically illustrates a first example diffuser case.

FIG. 4 schematically illustrates a second example diffuser case.

FIG. 5 schematically illustrates a third example diffuser case.

FIG. 6 schematically illustrates a fourth example diffuser case.

DETAILED DESCRIPTION OF AN EMBODIMENT

FIG. 1 schematically illustrates a gas turbine engine 20. The gasturbine engine 20 is disclosed herein as a two-spool turbofan thatgenerally incorporates a fan section 22, a compressor section 24, acombustor section 26 and a turbine section 28. Alternative engines mightinclude an augmentor section (not shown) among other systems orfeatures. The fan section 22 drives air along a bypass flowpath whilethe compressor section 24 drives air along a core flowpath forcompression and communication into the combustor section 26 thenexpansion through the turbine section 28. Although depicted as aturbofan gas turbine engine in the disclosed non-limiting embodiment, itshould be understood that the concepts described herein are not limitedto use with turbofans as the teachings may be applied to other types ofturbine engines including three-spool architectures.

The engine 20 generally includes a low speed spool 30 and a high speedspool 32 mounted for rotation about an engine central longitudinal axisA relative to an engine static structure 36 via several bearing systems38. It should be understood that various bearing systems 38 at variouslocations may alternatively or additionally be provided.

The low speed spool 30 generally includes an inner shaft 40 thatinterconnects a fan 42, a low pressure compressor 44 and a low pressureturbine 46. The inner shaft 40 is connected to the fan 42 through ageared architecture 48 to drive the fan 42 at a lower speed than the lowspeed spool 30. The high speed spool 32 includes an outer shaft 50 thatinterconnects a high pressure compressor 52 and high pressure turbine54. A combustor 56 is arranged between the high pressure compressor 52and the high pressure turbine 54. A mid-turbine frame 57 of the enginestatic structure 36 is arranged generally between the high pressureturbine 54 and the low pressure turbine 46. The mid-turbine frame 57further supports bearing systems 38 in the turbine section 28. The innershaft 40 and the outer shaft 50 are concentric and rotate via bearingsystems 38 about the engine central longitudinal axis A which iscollinear with their longitudinal axes.

The core airflow is compressed by the low pressure compressor 44 thenthe high pressure compressor 52, mixed and burned with fuel in thecombustor 56, then expanded over the high pressure turbine 54 and lowpressure turbine 46. The mid-turbine frame 57 includes airfoils 59 whichare in the core airflow path. The turbines 46, 54 rotationally drive therespective low speed spool 30 and high speed spool 32 in response to theexpansion.

The engine 20 in one example a high-bypass geared aircraft engine. In afurther example, the engine 20 bypass ratio is greater than about six(6), with an example embodiment being greater than ten (10), the gearedarchitecture 48 is an epicyclic gear train, such as a planetary gearsystem or other gear system, with a gear reduction ratio of greater thanabout 2.3 and the low pressure turbine 46 has a pressure ratio that isgreater than about five (5). In one disclosed embodiment, the engine 20bypass ratio is greater than about ten (10:1), the fan diameter issignificantly larger than that of the low pressure compressor 44, andthe low pressure turbine 46 has a pressure ratio that is greater thanabout five (5:1). Low pressure turbine 46 pressure ratio is pressuremeasured prior to inlet of low pressure turbine 46 as related to thepressure at the outlet of the low pressure turbine 46 prior to anexhaust nozzle. The geared architecture 48 may be an epicycle geartrain, such as a planetary gear system or other gear system, with a gearreduction ratio of greater than about 2.5:1. It should be understood,however, that the above parameters are only exemplary of one embodimentof a geared architecture engine and that the present invention isapplicable to other gas turbine engines including direct driveturbofans.

A significant amount of thrust is provided by the bypass flow B due tothe high bypass ratio. The fan section 22 of the engine 20 is designedfor a particular flight condition—typically cruise at about 0.8 Mach andabout 35,000 feet. The flight condition of 0.8 Mach and 35,000 ft, withthe engine at its best fuel consumption—also known as “bucket cruiseThrust Specific Fuel Consumption (‘TSFC’)”—is the industry standardparameter of lbm of fuel being burned divided by lbf of thrust theengine produces at that minimum point. “Low fan pressure ratio” is thepressure ratio across the fan blade alone, without a Fan Exit Guide Vane(“FEGV”) system. The low fan pressure ratio as disclosed hereinaccording to one non-limiting embodiment is less than about 1.45. “Lowcorrected fan tip speed” is the actual fan tip speed in ft/sec dividedby an industry standard temperature correction of [(Tram ° R)/(518.7°R)]^(0.5). The “Low corrected fan tip speed” as disclosed hereinaccording to one non-limiting embodiment is less than about 1150ft/second.

FIG. 2 is a sectional view 100 of the turbine engine 20 of FIG. 1,illustrating a high pressure compressor portion 102. The compressorportion 102 includes rotor blades 103 connected to rotor disks 104. Anexit guide vane 106 is positioned within the gas flow path C immediatelyaft of the compressor portion 102 and alters flow characteristics of agas flow exiting the compressor portion 102, prior to the gas flowentering a combustor 56 (illustrated in FIG. 1).

Immediately aft of the exit guide vane 106 and positioned in the gasflow path C is an inner diffuser case 108 that mechanically supports thestructures of the turbine engine 20. The inner diffuser case 108 isconnected on a radially interior edge to a turbine engine supportstructure via an inner skirt 110 and is connected to a turbine enginecase structure on a radially outer edge via a support cone 112.Integrally connected with the inner diffuser case 108 is an innerdiffuser case strut 109. The inner diffuser case strut 109 furtherincludes a flow path opening aligned with the gas flow path C, therebyallowing gasses in the flow path C to pass through the inner diffusercase strut 109. The inner diffuser case 108 is also connected on theradially outer edge to the turbine engine case structure via a secondwall 126.

Immediately superior of the support cone 112 is an upper mixing chamber122. The upper mixing chamber 122 is a cavity defined by the supportcone, the second wall 126 and the turbine engine case 128. In somealternate examples, the upper mixing chamber 122 can be replaced via amixing chamber disposed within the diffuser strut.

The upper mixing chamber 122 receives cooled air from a cooled air heatexchanger 120, and allows the cooled air to mix with ambient air, suchas air from the combustor section 26, to achieve a desired temperature.In one example, the cooled air received in the upper mixing chamber isovercooled air.

The upper mixing chamber 122 and the cooled air heat exchanger 120 arecollectively referred to as a cooled air system, and the cooled air fromthe cooled air system is distributed to turbine engine components thatneed cooling. In one example, the cooled air is provided to a TangentialOn Board Injection (TOBI) system 107. In another example, the cooled airis provided to an exit rim 105 of the compressor section 24. In anotherexample the cooled air is provided to a Compressor On Board Injection(COBI) system 109.

As a result of the above described T₃ temperatures, the gas exiting thecompressor portion 102 is at an extremely high temperature, and subjectsthe aftmost rotor blade attachment 103 and the compressor hub totemperatures elevated beyond the standard temperature capabilities ofthe respective parts. By providing a cooled air mixing chamber 122,cooling air can be mixed with ambient air and conditioned to a propercooling temperature prior to the cooled air being sent to the rotorblade's attachment 103, the spacer arm, and the compressor hub, therebyallowing the T₃ temperatures to be utilized.

FIG. 3 illustrates a first example inner diffuser case 200 in greaterdetail. As described and illustrated with regards to FIG. 2, the innerdiffuser case 200 includes an inner diffuser case strut 201 having foreedge 210 and an aft edge 216. An inner skirt 212 connects the diffuserstrut 201 to a radially inner support structure of the turbine engine20. Similarly, a support cone 214 structure connects the inner diffusercase strut 201 to the turbine engine case. An upper mixing chamber 220is defined radially outward of the inner diffuser case 200 and receivescooled air from a heat exchanger 221 located elsewhere in the turbineengine 20.

A second wall 240 connects the aft edge 216 of the strut 201 to theturbine engine case. The second wall 240 is formed from a flange 242extending radially outward from the strut 201 and a flange 244 extendingradially inward from the turbine engine case. The two flanges 242, 244define a gap that is sealed via a finger seal 246. The finger seal 246includes multiple local perforations or gaps that allow ambient air fromthe combustor section 26 to enter the upper mixing chamber 220. Thelocal perforations, or gaps, are metered (sized) to limit the amount ofairflow into the upper mixing chamber 220, thereby ensuring that adesired mixing of air from a heat exchanger 221 and air from thecombustor section 26 is achieved.

In the illustrated example, the finger seal 246 is fastened to the outerflange 244 via a fastener 245. The finger seal 246 is maintained inplace against the radially inner flange 242 by a naturally occurringspring pressure of the seal material. The sealing is further aided by apressure differential between the compressor section 24 and thecombustor section 26. The pressure differential also ensures that airfrom the upper mixing chamber 220 does not exit via the metering holesinto the combustor section 26.

The inner diffuser case strut 201 includes at least one air feed passage222. The air feed passage 222 has an opening 223 at the upper mixingchamber 220 that allows mixed air from the upper mixing chamber 220 toenter the air feed passage 222. The air feed passage 222 then directsthe mixed air to a turbine engine cooling system, such as a TOBI system,or any other cooling system.

With continued reference to FIG. 3, and with like numerals indicatinglike elements, FIG. 4 illustrates an alternate configuration fordefining the upper mixing chamber 220. As with the example of FIG. 3,the inner diffuser case 200 includes an inner diffuser case strut 201having fore edge 210 and an aft edge 216. An inner skirt 212 connectsthe diffuser strut 201 to a radially inner support structure of theturbine engine 20. Similarly, a support cone 214 structure connects theinner diffuser case strut 201 to the turbine engine case. An uppermixing chamber 220 is defined radially outward of the inner diffusercase 200 and receives cooled air from a heat exchanger 221 locatedelsewhere in the turbine engine 20.

A second wall 240 connects the aft edge 216 of the strut 201 to theturbine engine case and separates the upper mixing chamber 220 from anadjacent combustor section 26. The second wall 240 is integrally formedwith the strut 201 and is connected to the turbine engine case via anyknown fastening means. In alternate examples, the second wall 240 can beintegrally formed with the turbine case and connected to the strut 201via any known fastening means, or formed separately and connected toeach of the strut 201 and the turbine engine case. Further includedwithin the second wall 240 are multiple metered holes 310. The meteredholes 310 are sized to permit a desired airflow from the combustorsection 26 to enter the upper mixing chamber 220.

In order to utilize the solid second wall 240 without a gap (as in theexample of FIG. 3), consideration must be given to the thermal expansionand contraction of the various components. As such, the material fromwhich the second wall 240 is constructed should be selected by adesigner to accommodate for various expansions and contractions. Theexample of FIG. 4 is particularly suited to turbine engine environmentswhere the strut and turbine case have similar thermal expansion andcontraction rates, as such a design would include minimal thermalvariance between the strut 201 and the turbine engine case.

Once the air from the combustor section 26 enters the upper mixingchamber, it is mixed with the air from the heat exchanger 221 togenerate the desired mixed air for the corresponding cooling systems.Air is provided from the upper mixing chamber 220 to the cooledcomponents or cooling systems in the same manner as is described abovewith regards to the example of FIG. 3.

With continued reference to FIGS. 3 and 4, and with like numeralsindicating like elements, FIG. 5 illustrates a second alternateconfiguration for defining the upper mixing chamber 220. The example ofFIG. 5 is identical to the examples of FIGS. 3 and 4 with the exceptionof the second wall 240. In the alternate example of FIG. 5, the secondwall 240 is formed of three sections 410, 420, 430. A radially inwardsection 410 is integrally formed with the strut 201 and a radiallyoutward section 430 is formed as part of the turbine engine case. Eachof the inner and outer sections 410, 430 are formed of rigid materials.Typically these materials will be the same material as the strut 201 orthe turbine engine case. The middle section 420, is joined to each ofthe inner and outer sections 410, 430 and is formed of a flexiblematerial, such as a sheet metal. The flexible material allows for thesecond wall 240 to accommodate varied thermal expansion and contractionrates between the components by flexing and unflexing the middle section420 as necessary. The flexible middle segment 420 further includesmultiple holes 422. The holes 422 are metered to allow air from thecombustor section 26 into the upper mixing chamber 220 as describedabove with regard to the holes 310 in the example of FIG. 4, and achievethe same affect.

While no specific connection means is illustrated for connecting theflexible middle section 420 to the inner section 410 and the outersection 430, it is understood that one of skill in the art would be ableto utilize any number of standard connection schemes to achieve theillustrated embodiment.

In some turbine engines 20 it is desirable to locate a mixing chamberinternal to a strut 501. FIG. 6 illustrates an inner diffuser case 500in one such example. The inner diffuser case 500 includes an innerdiffuser case strut 501 having a fore edge 510 and an aft edge 516. Aninner skirt 512 connects the diffuser strut 501 to a radially innersupport structure of the turbine engine 20. Similarly, a support cone514 structure connects the inner diffuser case strut 501 to the turbineengine case. A mixing chamber 520 is defined within the strut 501 andreceives cooled air from a heat exchanger 521 located elsewhere in theturbine engine 20 via a cooled air inlet tube 530.

The cooled air inlet tube 530 protrudes through the inner diffuser case500 and enters the strut 501 via an opening 540. The opening 540 issealed around the cooled air inlet tube 530 via a ring seal. Inalternate configurations, the opening 540 can be sealed around thetubing via another known seal type.

The aft edge 516 of the strut 501 includes at least one hole 550 thatallows air from the combustor section 26 to enter the mixing chamber520. Once mixed, the air in the mixing chamber 520 is passed out of themixing chamber 520 via an opening 560 that connects the mixing chamber520 to a turbine engine cooling system.

While each of the above embodiments describes receiving air into themixing chambers from a heat exchanger system and a combustor section, itis understood that any appropriate source of air can be utilized, andthe designs are not limited to the specifically enumerated locations.

It is further understood that any of the above described concepts can beused alone or in combination with any or all of the other abovedescribed concepts. Although an embodiment of this invention has beendisclosed, a worker of ordinary skill in this art would recognize thatcertain modifications would come within the scope of this invention. Forthat reason, the following claims should be studied to determine thetrue scope and content of this invention.

The invention claimed is:
 1. A turbine engine comprising: a compressorsection; a combustor section in fluid communication with the compressorsection; a turbine section in fluid communication with the combustorsection; and a mixing chamber defined within a diffuser case strut,wherein the diffuser case strut is connected to a turbine engine casevia an inner diffuser case wall and the diffuser case strut is connectedto a radially inward engine support structure via at least an innerskirt; a cooled air inlet tube extends from said turbine engine caseinto said mixing chamber such that air entering the cooled air inlettube is deposited in the mixing chamber.
 2. The turbine engine of claim1, wherein the diffuser case strut is located within a primary fluidflow path connecting the compressor section, the combustor section, andthe turbine section.
 3. The turbine engine of claim 1, wherein an aftedge of the diffuser case strut is a mixing chamber wall and isolatesthe mixing chamber from ambient air in the combustor section.
 4. Theturbine engine of claim 3, wherein said mixing chamber wall includes atleast one metering hole operable to allow ambient air from an enginecomponent adjacent to the mixing chamber wall to enter the mixingchamber and mix with the air deposited from said inlet tube.
 5. Theturbine engine of claim 4, wherein said cooled air inlet tube includesan inlet opening for connecting to a bypass airflow passage such thatair from the bypass airflow passage enters the mixing chamber throughthe inlet tube, wherein the inlet opening is on an opposite end of theinlet tube relative to an outlet of said cooled air inlet tube, whereinsaid outlet of said cooled air inlet tube is in said mixing chamber. 6.The turbine engine of claim 1, wherein said mixing chamber furthercomprises an outlet opening operable to direct mixed air out of themixing chamber.
 7. The turbine engine of claim 6, wherein said outletopening directs the mixed air from the mixing chamber to at least oneturbine engine component.
 8. The turbine engine of claim 7, wherein saidturbine engine component is one of a tangential on board injectionsystem and a compressor on board injection system.